IRF Auflistung nach Autor:in "Prévôt, André S.H."

Auflistung nach Autor:in "Prévôt, André S.H."

Gerade angezeigt 1 - 20 von 20

A mobile pollutant measurement laboratory - measuring gas phase and aerosol ambient concentrations with high spatial and temporal resolution
(Elsevier, 12/2002) Bukowiecki, Nicolas; Dommen, Josef; Prévôt, André S.H.; Richter, Rene; Weingartner, Ernest; Baltensperger, Urs [in: Atmospheric Environment]
A mobile pollutant measurement laboratory was designed and built at the Paul Scherrer Institute (Switzerland) for the measurement of on-road ambient concentrations of a large set of trace gases and aerosol parameters with high time resolution (<15 s for most instruments), along with geographical and meteorological information. This approach allowed for pollutant level measurements both near traffic (e.g. in urban areas or on freeways/main roads) and at rural locations far away from traffic, within short periods of time and at different times of day and year. Such measurements were performed on a regular base during the project year of gas phase and aerosol measurements (YOGAM). This paper presents data measured in the Zürich (Switzerland) area on a late autumn day (6 November) in 2001. The local urban particle background easily reached 50 000 cmˉ³, with additional peak particle number concentrations of up to 400 000 cmˉ³. The regional background of the total particle number concentration was not found to significantly correlate with the distance to traffic and anthropogenic emissions of carbon monoxide and nitrogen oxides. On the other hand, this correlation was significant for the number concentration of particles in the size range 50–150 nm, indicating that the particle number concentration in this size range is a better traffic indicator than the total number concentration. Particle number size distribution measurements showed that daytime urban ambient air is dominated by high number concentrations of ultrafine particles (nanoparticles) with diameters < 50 nm, which are immediately formed by traffic exhaust and thus belong to the primary emissions. However, significant variation of the nanoparticle mode was also observed in number size distributions measured in rural areas both at daytime and nighttime, suggesting that nanoparticles are not exclusively formed by primary traffic emissions. While urban daytime total number concentrations were increased by a factor of 10 compared to the nighttime background, corresponding factors for total surface area and total volume concentrations were 2 and 1.5, respectively.
01A - Beitrag in wissenschaftlicher Zeitschrift
A new method to discriminate secondary organic aerosols from different sources using high-resolution aerosol mass spectra
(Copernicus, 2012) Heringa, Maarten F.; DeCarlo, Peter F.; Chirico, Roberto; Tritscher, Torsten; Clairotte, Michael; Mohr, Christine; Crippa, Monica; Slowik, Jay Gates; Pfaffenberger, Lisa; Dommen, Josef; Weingartner, Ernest; Prévôt, André S.H.; Baltensperger, Urs [in: Atmospheric Chemistry and Physics]
Abstract. Organic aerosol (OA) represents a significant and often major fraction of the non-refractory PM1 (particulate matter with an aerodynamic diameter da < 1 μm) mass. Secondary organic aerosol (SOA) is an important contributor to the OA and can be formed from biogenic and anthropogenic precursors. Here we present results from the characterization of SOA produced from the emissions of three different anthropogenic sources. SOA from a log wood burner, a Euro 2 diesel car and a two-stroke Euro 2 scooter were characterized with an Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-TOF-AMS) and compared to SOA from α-pinene. The emissions were sampled from the chimney/tailpipe by a heated inlet system and filtered before injection into a smog chamber. The gas phase emissions were irradiated by xenon arc lamps to initiate photo-chemistry which led to nucleation and subsequent particle growth by SOA production. Duplicate experiments were performed for each SOA type, with the averaged organic mass spectra showing Pearson's r values >0.94 for the correlations between the four different SOA types after five hours of aging. High-resolution mass spectra (HR-MS) showed that the dominant peaks in the MS, m/z 43 and 44, are dominated by the oxygenated ions C2H3O+ and CO2+, respectively, similarly to the relatively fresh semi-volatile oxygenated OA (SV-OOA) observed in the ambient aerosol. The atomic O:C ratios were found to be in the range of 0.25–0.55 with no major increase during the first five hours of aging. On average, the diesel SOA showed the lowest O:C ratio followed by SOA from wood burning, α-pinene and the scooter emissions. Grouping the fragment ions revealed that the SOA source with the highest O:C ratio had the largest fraction of small ions. The HR data of the four sources could be clustered and separated using principal component analysis (PCA). The model showed a significant separation of the four SOA types and clustering of the duplicate experiments on the first two principal components (PCs), which explained 79% of the total variance. Projection of ambient SV-OOA spectra resolved by positive matrix factorization (PMF) showed that this approach could be useful to identify large contributions of the tested SOA sources to SV-OOA. The first results from this study indicate that the SV-OOA in Barcelona is strongly influenced by diesel emissions in winter while in summer at SIRTA at the southwestern edge of Paris SV-OOA is more similar to alpha-pinene SOA. However, contributions to the ambient SV-OOA from SOA sources that are not covered by the model can cause major interference and therefore future expansions of the PCA model with additional SOA sources is recommended.
01A - Beitrag in wissenschaftlicher Zeitschrift
A study of wood burning and traffic aerosols in an Alpine valley using a multi-wavelength aethalometer
(Elsevier, 20.09.2008) Sandradewi, Jisca; Prévôt, André S.H.; Weingartner, Ernest; Schmidhauser, Ralph; Gysel, Martin; Baltensperger, Urs [in: Atmospheric Environment]
We present a study of aerosol light absorption using a multi-wavelength Aethalometer (l ¼ 370–950 nm) in an Alpine valley where the major local emissions of aerosols in winter are from domestic wood burning and traffic. The measurements were done in winter and summer periods in 2004 and 2005. Much stronger diurnal trends in CO, NOx and aerosol light absorption parameters were observed in winter than in summer. The average (71 S.D.) PM10 concentrations measured at this site were 31.5721.7 mg m 3 in winter and 15.8710.0 mg m 3 in summer. The highest PM10 concentrations were observed between 18:00 and 22:00 h CET in both campaigns, with 45.4721.0 mg m 3 for winter and 21.079.5 mg m 3 for summer. The average (71 S.D.) power law exponents of the absorption coefficients (also called absorption exponent) with l ¼ 370–950 nm, a370–950 nm were 1.670.25 in winter and 1.170.05 in summer. The calculation of a separately for lower and higher wavelengths (i.e., a370–520 nm and a660–950 nm) provided a better description of the wavelength dependence from the UV- to the near-IR region. The highest mean values of a370–520 nm and a660–950 nm were observed between 22:00 and 02:00 h CET in winter with 2.770.4 and 1.370.1, respectively. Comparison of a370–520 nm with CO and NOx data indicated that the relative contribution of wood burning versus traffic was responsible for the seasonal and diurnal variability of a. The seasonal and diurnal trends of a were not attributed to changes in the particle size since the aerosol volume size distributions (dV/d log D) were found to be similar in both campaigns.
01A - Beitrag in wissenschaftlicher Zeitschrift
Aerosol and NOx emission factors and submicron particle number size distributions in two road tunnels with different traffic regimes
(Copernicus, 21.06.2006) Imhof, David; Weingartner, Ernest; Prévôt, André S.H.; Ordóñez, Carlos; Kurtenbach, Ralf; Wiesen, Peter; Rodler, Johannes; Sturm, Peter; McCrae, Ian; Ekström, M.; Baltensperger, Urs [in: Atmospheric Chemistry and Physics]
Measurements of aerosol particle number size distributions (18–700 nm), mass concentrations (PM2.5 and PM10) and NOx were performed in the Plabutsch tunnel, Austria, and in the Kingsway tunnel, United Kingdom. These two tunnels show different characteristics regarding the roadway gradient, the composition of the vehicle fleet and the traffic frequency. The submicron particle size distributions contained a soot mode in the diameter range D=80–100 nm and a nucleation mode in the range of D=20–40 nm. In the Kingsway tunnel with a significantly lower particle number and volume concentration level than in the Plabutsch tunnel, a clear diurnal variation of nucleation and soot mode particles correlated to the traffic density was observed. In the Plabutsch tunnel, soot mode particles also revealed a diurnal variation, whereas no substantial variation was found for the nucleation mode particles. During the night a higher number concentration of nucleation mode particles were measured than soot mode particles and vice versa during the day. In this tunnel with very high soot emissions during daytime due to the heavy-duty vehicle (HDV) share of 18% and another 40% of diesel driven light-duty vehicles (LDV) semivolatile species condense on the pre-existing soot surface area rather than forming new particles by homogeneous nucleation. With the low concentration of soot mode particles in the Kingsway tunnel, also the nucleation mode particles exhibit a diurnal variation. From the measured parameters real-world traffic emission factors were estimated for the whole vehicle fleet as well as differentiated into the two categories LDV and HDV. In the particle size range D=18–700 nm, each vehicle of the mixed fleet emits (1.50±0.08)×10^14 particles km-1 (Plabutsch) and (1.26±0.10)×10^14 particles km-1 (Kingsway), while particle volume emission factors of 0.209±0.008 cm³ km-1 and 0.036±0.004 cm³ km-1, respectively, were obtained. PM1 emission factors of 104±4 mg km-1 (Plabutsch) and 41±4 mg km-1 (Kingsway) were calculated. Emission factors determined in this work were in good agreement with results from other studies.
01A - Beitrag in wissenschaftlicher Zeitschrift
Ambient and laboratory observations of organic ammonium salts in PM₁
(Royal Society of Chemistry, 2017) Schlag, Patrick; Rubach, Florian; Mentel, Thomas F.; Reimer, David Thomas; Canonaco, Francesco; Henzing, Bas; Moerman, M.; Otjes, R.; Prévôt, André S.H.; Rohrer, Franz; Rosati, B.; Tillmann, Ralf; Weingartner, Ernest; Kiendler-Scharr, Astrid [in: Faraday Discussions]
Ambient measurements of PM₁aerosol chemical composition at Cabauw, the Netherlands, implicate higher ammonium concentrations than explained by the formation of inorganic ammonium salts. This additional particulate ammonium is called excess ammonium (e_NH4). Height profiles over the Cabauw Experimental Site for Atmospheric Research (CESAR) tower, of combined ground based and airborne aerosol mass spectrometric (AMS) measurements on a Zeppelin airship show higher concentrations ofe_NH4at higher altitudes compared to the ground. Through flights across the Netherlands, the Zeppelin based measurements furthermore substantiatee_NH4as a regional phenomenon in the planetary boundary layer. The excess ammonium correlates with mass spectral signatures of (di-)carboxylic acids, making a heterogeneous acid–base reaction the likely process of NH₃uptake. We show that this excess ammonium was neutralized by the organic fraction forming particulate organic ammonium salts. We discuss the significance of such organic ammonium salts for atmospheric aerosols and suggest that NH₃emission control will have benefits for particulate matter control beyond the reduction of inorganic ammonium salts.
01A - Beitrag in wissenschaftlicher Zeitschrift
Analysis of the hygroscopic and volatile properties of ammonium sulphate seeded and unseeded SOA particles
(Copernicus, 28.01.2009) Meyer, Nic K.; Duplissy, Jonathan; Gysel, Martin; Metzger, Axel; Dommen, Josef; Weingartner, Ernest; Alfarra, Rami; Prévôt, André S.H.; Fletcher, C; Good, Nicholas; McFiggans, Gordan; Jonsson, Åsa M.; Hallquist, Mattias; Baltensperger, Urs; Ristovski, Zoran D. [in: Atmospheric Chemistry and Physics]
The volatile and hygroscopic properties of ammonium sulphate seeded and unseeded secondary organic aerosol (SOA) derived from the photo-oxidation of atmospherically relevant concentrations of α-pinene were studied. The seed particles were electrospray generated ammonium sulphate ((NH4)2SO4) having diameters of approximately 33 nm with a quasi-mono-disperse size distribution (geometric standard deviation σg=1.3). The volatile and hygroscopic properties of both seeded and unseeded SOA were simultaneously measured with a VH-TDMA (volatility – hygroscopicity tandem differential mobility analyzer). VH-TDMA measurements of unseeded SOA show a decrease in the hygroscopic growth (HGF) factor for increased volatilisation temperatures such that the more volatile compounds appear to be more hygroscopic. This is opposite to the expected preferential evaporation of more volatile but less hygroscopic material, but could also be due to enhanced oligomerisation occurring at the higher temperature in the thermodenuder. In addition, HGF measurements of seeded SOA were measured as a function of time at two relative humidities, below (RH 75%) and above (RH 85%) the deliquescence relative humidity (DRH) of the pure ammonium sulphate seeds. As these measurements were conducted during the onset phase of photo-oxidation, during particle growth, they enabled us to find the dependence of the HGF as a function of the volume fraction of the SOA coating. HGF's measured at RH of 85% showed a continuous decrease as the SOA coating thickness increased. The measured growth factors show good agreements with ZSR predictions indicating that, at these RH values, there are only minor solute-solute interactions. At 75% RH, as the SOA fraction increased, a rapid increase in the HGF was observed indicating that an increasing fraction of the (NH4)2SO4 is subject to a phase transition, going into solution, with an increasing volume fraction of SOA. To our knowledge this is the first time that SOA derived from photo-oxidised α-pinene has been shown to affect the equilibrium water content of inorganic aerosols below their DRH. For SOA volume fractions above ~0.3 the measured growth factor followed roughly parallel to the ZSR prediction based on fully dissolved (NH4)2SO4 although with a small difference that was just larger than the error estimate. Both incomplete dissolution and negative solute-solute interactions could be responsible for the lower HGF observed compared to the ZSR predictions.
01A - Beitrag in wissenschaftlicher Zeitschrift
Black carbon physical properties and mixing state in the European megacity Paris
(Copernicus, 2013) Laborde, Marie; Crippa, Monica; Tritscher, Torsten; Jurányi, Zsófia; Decarlo, Peter; Temime-Roussel, Brice; Marchand, Nicolas; Eckhardt, Sabine; Stohl, Andreas; Baltensperger, Urs; Prévôt, André S.H.; Weingartner, Ernest; Gysel, Martin [in: Atmospheric Chemistry and Physics]
Aerosol hygroscopicity and refractory black carbon (rBC) properties were characterised during wintertime at a suburban site in Paris, one of the biggest European cities. Hygroscopic growth factor (GF) frequency distributions, characterised by distinct modes of more-hygroscopic background aerosol and non- or slightly hygroscopic aerosol of local (or regional) origin, revealed an increase of the relative contribution of the local sources compared to the background aerosol with decreasing particle size. BC-containing particles in Paris were mainly originating from fresh traffic emissions, whereas biomass burning only gave a minor contribution. The mass size distribution of the rBC cores peaked on average at an rBC core mass equivalent diameter of DMEV ~ 150 nm. The BC-containing particles were moderately coated (coating thickness Δcoat ~ 33 nm on average for rBC cores with DMEV = 180–280 nm) and an average mass absorption coefficient (MAC) of ~ 8.6 m2 g−1 at the wavelength λ = 880 nm was observed. Different time periods were selected to investigate the properties of BC-containing particles as a function of source and air mass type. The traffic emissions were found to be non-hygroscopic (GF ≈ 1.0), and essentially all particles with a dry mobility diameter (D0) larger than D0 = 110 nm contained an rBC core. rBC from traffic emissions was further observed to be uncoated within experimental uncertainty (Δcoat ~ 2 nm ± 10 nm), to have the smallest BC core sizes (maximum of the rBC core mass size distribution at DMEV ~ 100 nm) and to have the smallest MAC (~ 7.3 m2g−1 at λ = 880 nm). The biomass burning aerosol was slightly more hygroscopic than the traffic emissions (with a distinct slightly-hygroscopic mode peaking at GF ≈ 1.1–1.2). Furthermore, only a minor fraction (&leq; 10%) of the slightly-hygroscopic particles with 1.1 &leq; GF &leq; 1.2 (and D0 = 265 nm) contained a detectable rBC core. The BC-containing particles from biomass burning were found to have a medium coating thickness as well as slightly larger mean rBC core sizes and MAC values compared to traffic emissions. The aerosol observed under the influence of aged air masses and air masses from Eastern Continental Europe was dominated by a~more-hygroscopic mode peaking at GF ≈ 1.6. Most particles (95%), in the more-hygroscopic mode at D0 = 265 nm, did not contain a detectable rBC core. A significant fraction of the BC-containing particles had a substantial coating with non-refractory aerosol components. MAC values of ~ 8.8 m2g−1 and ~ 8.3 m2g−1 at λ = 880 nm and mass mean rBC core diameters of 150 nm and 200 nm were observed for the aged and continental air mass types, respectively. The reason for the larger rBC core sizes compared to the fresh emissions – transport effects or a different rBC source – remains unclear. The dominant fraction of the BC-containing particles was found to have no or very little coating with non-refractory matter. The lack of coatings is consistent with the observation that the BC-containing particles are non- or slightly-hygroscopic, which makes them poor cloud condensation nuclei. It can therefore be expected that wet removal through nucleation scavenging is inefficient for fresh BC-containing particles in urban plumes. The mixing-state-specific cloud droplet activation behaviour of BC-containing particles including the effects of atmospheric aging processes should be considered in global simulations of atmospheric BC, as the wet removal efficiency remains a major source of uncertainty in its life-cycle.
01A - Beitrag in wissenschaftlicher Zeitschrift
Changes of hygroscopicity and morphology during ageing of diesel soot
(Institute of Physics Publishing, 2011) Tritscher, Torsten; Jurányi, Zsófia; Martin, Maria; Chirico, Roberto; Gysel, Martin; Heringa, Maarten F.; DeCarlo, Peter F.; Sierau, Berko; Prévôt, André S.H.; Weingartner, Ernest; Baltensperger, Urs [in: Environmental Research Letters]
01A - Beitrag in wissenschaftlicher Zeitschrift
Cloud forming potential of secondary organic aerosol under near atmospheric conditions
(Wiley, 2008) Duplissy, Jonathan; Gysel, Martin; Alfarra, M. Rami; Dommen, Josef; Metzger, Axel; Prévôt, André S.H.; Weingartner, Ernest; Laaksonen, Ari; Raatikainen, Tomi; Good, Nicholas; Turner, S. Fiona; McFiggans, Gordon; Baltensperger, Urs [in: Geophysical Research Letters]
Cloud droplets form by nucleation on atmospheric aerosol particles. Populations of such particles invariably contain organic material, a major source of which is thought to be condensation of photo‐oxidation products of biogenic volatile organic compounds (VOCs). We demonstrate that smog chamber studies of the formation of such biogenic secondary organic aerosol (SOA) formed during photo‐oxidation must be conducted at near atmospheric concentrations to yield atmospherically representative particle composition, hygroscopicity and cloud‐forming potential. Under these conditions, the hygroscopicity measured at 95% relative humidity can be used reliably to predict the CCN activity of the SOA particles by assuming droplet surface tension of pure water. We also show that the supersaturation required to activate a given size of particle decreases with age.
01A - Beitrag in wissenschaftlicher Zeitschrift
Evidence for the role of organics in aerosol particle formation under atmospheric conditions
(National Academy of Sciences, 19.01.2010) Metzger, Axel; Verheggen, Bart; Dommen, Josef; Duplissy, Jonathan; Prévôt, André S.H.; Weingartner, Ernest; Riipinen, Ilona; Kulmala, Markku; Spracklen, Dominick V.; Carslaw, Kenneth S.; Baltensperger, Urs [in: Proceedings of the National Academy of Sciences of the United States of America]
New particle formation in the atmosphere is an important parameter in governing the radiative forcing of atmospheric aerosols. However, detailed nucleation mechanisms remain ambiguous, as laboratory data have so far not been successful in explaining atmospheric nucleation. We investigated the formation of new particles in a smog chamber simulating the photochemical formation of H2SO4 and organic condensable species. Nucleation occurs at H2SO4 concentrations similar to those found in the ambient atmosphere during nucleation events. The measured particle formation rates are proportional to the product of the concentrations of H2SO4 and an organic molecule. This suggests that only one H2SO4 molecule and one organic molecule are involved in the rate-limiting step of the observed nucleation process. Parameterizing this process in a global aerosol model results in substantially better agreement with ambient observations compared to control runs.
01A - Beitrag in wissenschaftlicher Zeitschrift
Evolution of nanoparticle composition in CLOUD in presence of sulphuric acid, ammonia and organics
(AIP Publishing, 24.06.2013) Keskinen, Helmi; Virtanen, Annele; Joutsensaari, Jorma; Tsagkogeorgas, Georgios; Duplissy, Jonathan; Schobesberger, Siegfried; Gysel, Martin; Riccobono, Francesco; Slowik, Jay Gates; Bianchi, Federico; Yli-Juuti, Taina; Lehtipalo, Katrianne; Rondo, Linda; Breitenlechner, Martin; Kupc, Agnieszka; Almeida, João; Amorim, Antonio; Dunne, Eimear M.; Downard, Andrew J.; Ehrhart, Sebastian; Franchin, Alessandro; Kajos, Maija K.; Kirkby, Jasper; Kürten, Andreas; Nieminen, Tuomo; Makhmutov, Vladimir; Mathot, Serge; Miettinen, Pasi; Onnela, Antti; Petäjä, Tuukka; Praplan, Arnaud; Santos, Filipe D.; Schallhart, Simon; Sipilä, Mikko; Stozhkov, Yuri; Tomé, Antonio; Vaattovaara, Petri; Wimmer, Daniela; Prévôt, André S.H.; Dommen, Josef; Donahue, Neil M.; Flagan, Richard C.; Viisanen, Yrjö; Weingartner, Ernest; Riipinen, Ilona; Hansel, Armin; Curtius, Joachim; Kulmala, Markku; Worsnop, Douglas R.; Baltensperger, Urs; Wex, Heike; Stratmann, Frank; Laaksonen, Ari; DeMott, Paul J.; O'Dowd, Colin D. [in: Nucleation and atmospheric aerosols]
04B - Beitrag Konferenzschrift
Fine and ultrafine particles in the Zürich (Switzerland) area measured with a mobile laboratory: an assessment of the seasonal and regional variation throughout a year
(Copernicus, 24.09.2003) Bukowiecki, Nicolas; Dommen, Josef; Prévôt, André S.H.; Weingartner, Ernest; Baltensperger, Urs [in: Atmospheric Chemistry and Physics]
On occasion of the project YOGAM (year of gas phase and aerosol measurements), the spatial and temporal variation of selected aerosol and gas phase parameters was assessed for the Zürich (Switzerland) area with a new mobile pollutant measurement laboratory. This assessment based on on-road measurements along a specified route on selected days during different seasons in 2001/2002, covering urban, suburban and rural regions. Special focus was put on the investigation and characterization of particles in the fine (particle diameter D<2.5 mm) and ultrafine (D<100 nm) size ranges. Analysis of Variance (ANOVA) showed that the variance of all considered fine and ultrafine aerosol parameters (i.e. particle background and total number concentration for particles larger than 3 nm, number concentrations in the size ranges 7-30 nm and 80-140 nm, as well as the active surface area concentration) was significantly larger for day-to-day than for spatial variation. However, Principal Component Analysis (PCA) found a similar regional pollution pattern within every single measuring day. Lowest particle background levels (D>3 nm) were found in rural areas at higher elevation (15 000 cmˉ³), while corresponding mean background values for urban and freeway-influenced areas were typically 35 000 cmˉ³ and >80 000 cmˉ³, respectively. Meteorology, i.e. prevailing weather conditions not only governed the day-to-day concentration variations in the selected area, but also influenced the formation of primary (directly traffic-related) and in few cases secondary (biogenic or anthropogenic) ultrafine particles. Overall, low temperatures regularly enhanced primary ultrafine particle formation in urban areas. There was a possible indication for relatively low number concentrations of secondary ultrafine particles during a few warm and sunny spring days. Mobile measurements as they were performed in this study have been shown to be suitable for pollutant assessments to obtain good information on spatial and day-to-day variability. For experimental studies concerning spatial resolution on a relatively short time scale (<1 day), a mobile measurement design may even be more appropriate than a network of stationary measuring sites.
01A - Beitrag in wissenschaftlicher Zeitschrift
Hygroscopic properties of fresh and aged wood burning particles
(Elsevier, 2013) Martin, Maria; Tritscher, Torsten; Jurányi, Zsófia; Heringa, Maarten F.; Sierau, Berko; Weingartner, Ernest; Chirico, Roberto; Gysel, Martin; Prévôt, André S.H.; Baltensperger, Urs; Lohmann, Ulrike [in: Journal of Aerosol Science]
01A - Beitrag in wissenschaftlicher Zeitschrift
Identification of polymers as major components of atmospheric organic aerosols
(Springer, 2004) Kalberer, Markus; Paulsen, Dwane; Sax, Mirjam; Steinbacher, Martin; Dommen, Josef; Prévôt, André S.H.; Fisseha, Rebeka; Weingartner, Ernest; Frankevich, Vladimir; Zenobi, Renato; Baltensperger, Urs [in: Science]
Results from photooxidation of aromatic compounds in a reaction chamber show that a substantial fraction of the organic aerosol mass is composed of polymers. This polymerization results from reactions of carbonyls and their hydrates. After aging for more than 20 hours, about 50% of the particle mass consists of polymers with a molecular mass up to 1000 daltons. This results in a lower volatility of this secondary organic aerosol and a higher aerosol yield than a model using vapor pressures of individual organic species would predict.
01A - Beitrag in wissenschaftlicher Zeitschrift
Investigations of primary and secondary particulate matter of different wood combustion appliances with a high-resolution time-of-flight aerosol mass spectrometer
(Copernicus, 23.06.2011) Heringa, Maarten F.; DeCarlo, Peter F.; Chirico, Roberto; Tritscher, Torsten; Dommen, Josef; Weingartner, Ernest; Richter, René; Wehrle, Günther; Prévôt, André S.H.; Baltensperger, Urs [in: Atmospheric Chemistry and Physics]
A series of photo-oxidation smog chamber experiments were performed to investigate the primary emissions and secondary aerosol formation from two different log wood burners and a residential pellet burner under different burning conditions: starting and flaming phase. Emissions were sampled from the chimney and injected into the smog chamber leading to primary organic aerosol (POA) concentrations comparable to ambient levels. The composition of the aerosol was measured by an Aerodyne high resolution time-of-flight aerosol mass spectrometer (HR-TOF-AMS) and black carbon (BC) instrumentation. The primary emissions were then exposed to xenon light to initiate photo-chemistry and subsequent secondary organic aerosol (SOA) production. After correcting for wall losses, the average increase in organic matter (OM) concentrations by SOA formation for the starting and flaming phase experiments with the two log wood burners was found to be a factor of 4.1±1.4 after five hours of aging. No SOA formation was observed for the stable burning phase of the pellet burner. The startup emissions of the pellet burner showed an increase in OM concentration by a factor of 3.3. Including the measured SOA formation potential, average emission factors of BC+POA+SOA, calculated from CO2 emission, were found to be in the range of 0.04 to 3.9 g/kg wood for the stable burning pellet burner and an old log wood burner during startup respectively. SOA contributed significantly to the ion C2H4O2+ at mass to charge ratio m/z 60, a commonly used marker for primary emissions of wood burning. This contribution at m/z 60 can overcompensate for the degradation of levoglucosan leading to an overestimation of the contribution of wood burning or biomass burning to the total OM. The primary organic emissions from the three different burners showed a wide range in O:C atomic ratio (0.19−0.60) for the starting and flaming conditions, which also increased during aging. Primary wood burning emissions have a rather low relative contribution at m/z 43 (f 43) to the total organic mass spectrum. The non-oxidized fragment C3H7+ has a considerable contribution at m/z 43 for the fresh OA with an increasing contribution of the oxygenated ion C2H3O+ during aging. After five hours of aging, the OA has a rather low C2H3O+ signal for a given CO2+ fraction, possibly indicating a higher ratio of acid to non-acid oxygenated compounds in wood burning OA compared to other oxygenated organic aerosol (OOA).
01A - Beitrag in wissenschaftlicher Zeitschrift
Laboratory observation of oligomers in the aerosol from isoprene/NOₓ photooxidation
(Wiley, 2006) Dommen, Josef; Metzger, Axel; Duplissy, Jonathan; Kalberer, Markus; Alfarra, M. Rami; Gascho, Astrid; Weingartner, Ernest; Prévôt, André S.H.; Verheggen, Bart; Baltensperger, Urs [in: Geophysical Research Letters]
Compounds assigned to be oxidation products of isoprene (2-methyl-1,3-butadiene) have recently been observed in ambient aerosols, suggesting that isoprene might play an important role in secondary organic aerosol (SOA) formation due to its large global source strength. SOA yields from photooxidation of isoprene and NOₓ in a chamber agree fairly well with previous data. Matrix assisted laser desorption/ionization mass spectrometry showed the formation of high molecular weight compounds over the course of 15-hour experiments. Concurrently, the volatility of the SOA decreased markedly as observed by a tandem differential mobility analyzer. The volume fraction remaining of SOA at 150°C increased steadily from 5 to 25% during the same experiments. These observations are attributed to oligomerization reactions occurring in the aerosol phase. Under dry conditions a lower volatility was observed.
01A - Beitrag in wissenschaftlicher Zeitschrift
Roadside measurements of particulate matter size distribution
(Elsevier, 10/2003) Sturm, Peter J.; Baltensperger, Urs; Bacher, Michael; Lechner, Bernhard; Hausberger, Stefan; Heiden, Bernhard; Imhof, David; Weingartner, Ernest; Prévôt, André S.H.; Kurtenbach, Ralf; Wiesen, Peter [in: Atmospheric Environment]
Roadside measurements were performed in order to document the size distribution of particulate matter (PM) under dilution conditions similar to those found in real world. These activities covered measurements at engine test beds, at different locations in a road tunnel as well as in an urban environment. In order to get a clear picture of the evolution of the PM in different size classes, the in-tunnel locations ranged from curb-side to different locations inside the exhaust air system. Additional measurements were performed in the ambient air at curb-side at a street crossing as well as in urban background. At those times when heavy traffic occurs, tunnel measurements show size distributions similar to those derived from engine/vehicle measurements. During times with little traffic the size distributions are closer to those recorded in ambient air. As soon as the traffic load increases the size distribution changes, due to rapid coagulation of the smallest particles with the accumulation mode. As the travel time of the particles through the tunnel and up the stacks is very long “aging” effects could be observed. Thus, these spectra are quite different from ambient measurements in urban air, especially in the region above 30–40 nm.
01A - Beitrag in wissenschaftlicher Zeitschrift
Secondary organic aerosol formation by irradiation of 1,3,5-trimethylbenzene−NOₓ-H2O in a new reaction chamber for atmospheric chemistry and physics
(American Chemical Society, 12.03.2005) Paulsen, Dwane; Dommen, Josef; Kalberer, Markus; Prévôt, André S.H.; Richter, René; Sax, Mirjam; Steinbacher, Martin; Weingartner, Ernest; Baltensperger, Urs [in: Environmental Science & Technology]
A new environmental reaction smog chamber was built to simulate particle formation and growth similar to that expected in the atmosphere. The organic material is formed from nucleation of photooxidized organic compounds. The chamber is a 27 m³ fluorinated ethylene propylene (FEP) bag suspended in a temperature-controlled enclosure. Four xenon arc lamps (16 kW total) are used to irradiate primary gas components for experiments lasting up to 24 h. Experiments using irradiations of 1,3,5-trimethylbenzene−NOₓ−H2O at similar input concentrations without seed particles were used to determine particle number and volume concentration wall loss rates of 0.209 ± 0.018 and 0.139 ± 0.070 1/h, respectively. The particle formation was compared with and without propene.
01A - Beitrag in wissenschaftlicher Zeitschrift
Secondary organic aerosols from anthropogenic and biogenic precursors
(Royal Society of Chemistry, 2005) Baltensperger, Urs; Kalberer, Markus; Dommen, Josef; Paulsen, Dwane; Alfarra, M. Rami; Coe, Hugh; Fisseha, Rebeka; Gascho, Astrid; Gysel, Martin; Nyeki, Stephan; Sax, Mirjam; Steinbacher, Martin; Prévôt, André S.H.; Sjögren, Staffan; Weingartner, Ernest; Zenobi, Renato [in: Faraday Discussions]
Secondary organic aerosol (SOA) formation from the photooxidation of an anthropogenic (1,3,5-trimethylbenzene) and a biogenic (α-pinene) precursor was investigated at the new PSI smog chamber. The chemistry of the gas phase was followed by proton transfer reaction mass spectrometry, while the aerosol chemistry was investigated with aerosol mass spectrometry, ion chromatography, laser desorption ionization mass spectrometry, and infrared spectroscopy, along with volatility and hygroscopicity studies. Evidence for oligomer formation for SOA from both precursors was given by an increasing abundance of compounds with a high molecular weight (up to 1000 Da) and by an increasing thermal stability with increasing aging time. The results were compared to data obtained from ambient aerosol samples, revealing a number of similar features.
01A - Beitrag in wissenschaftlicher Zeitschrift
Urban and rural aerosol characterization of summer smog events during the PIPAPO field campaign in Milan, Italy
(Wiley, 2002) Baltensperger, Urs; Streit, Niklaus; Weingartner, Ernest; Nyeki, Stephan; Prévôt, André S.H.; Van Dingenen, Rita; Virkkula, Aki; Putaud, Jean-Philippe; Even, A.; ten Brink, Harry; Blatter, Andreas; Neftel, Albrecht; Gäggeler, Heinz W. [in: Journal of Geophysical Research: Atmospheres]
A comprehensive range of aerosol parameters was measured at an urban and a rural site in the Milan, Italy metropolitan region during summer smog events in summer 1998. Measurements were performed as part of the Pianura Padana Produzione di Ozono (PIPAPO) field campaign to determine the sensitivity of O3 production to NOₓ and volatile organic carbon concentrations at several ground stations. Primary aerosol parameters (i.e., direct emissions) such as aerosol black carbon showed a distinct diurnal variation with maxima at about 0000 and 0800 central European summer time (CEST), in contrast to secondary aerosol parameters such as sulfate and nitrate. Aerosol number size distributions were measured under ambient conditions as well as after conditioning with volatility and hygroscopicity systems. A mode at d = 20–30 nm in the number concentration was found at 0800 CEST and exhibited high volatility at 110°C (∼80% volume lost upon heating) but no hygroscopic behavior. Based on these measurements, small particles (d < 40 nm) are thought to consist mainly of hydrophobic particulate organic matter, rather than soot or H2SO4 aerosols. Two distinct hygroscopic modes with average growth factors d/d0 ∼ 1.02 and 1.21–1.28 were found for particles with dry (relative humidity of <30%) diameters d0 = 50–200 nm. Submicrometer aerosols exhibited lower volatility at the rural than at the urban site, which is attributed to additional particulate mass produced by secondary particle formation.
01A - Beitrag in wissenschaftlicher Zeitschrift

Auflistung nach Autor:in "Prévôt, André S.H."

Treffer pro Seite

Sortieroptionen